That's the ONLY way we make pizza all summer long...as my oven RARELY gets turned on. I get those premade crusts, top it with our favorites and pre-heat the grill on high. Just before I put the pizzas on, I turn it down to low and put them on. Then, I put the cover on for about 5-10 minutes before checking them and turning them if they need.
Just make sure there are no flare ups when you put the pizza on the grill or you'll end up with a burnt pizza.
We put ours directly onto the grill and it works well.